Background: The standard of care when treating melanoma in situ (MMIS) is an excision with at least 5 mm surgical margins.1 Some studies have suggested up to 9 mm margins to maximize local recurrence-free survival.2 This retrospective review aims to assess the efficacy of imiquimod as a topical treatment for persistently positive MMIS at the margins of prior excisions or where surgery is not an option.
Methods: Retrospective study conducted at Moffitt Cancer Center between 2019 and 2021 with patients aged > 18 years with MMIS at the margins of excision of an invasive melanoma or MMIS. Included patients were not ideal candidates for primary or additional surgical resection due to non-feasibility of surgery because of comorbidity or cosmetically sensitive location and/or the need for repeated skin grafting, or due to patient's refusal. Patients received imiquimod on protocol for 16 weeks and were monitored for treatment response and side effects. Following completion of the treatment, scouting biopsies were performed to assess histological response, and dermoscopy was used to determine the clinical disease status.
Results: Ten patients completed 16 weeks of imiquimod. Seven (75%) had a median of 2 surgical resections, and 3 refused surgery despite discussion that surgery was standard of care. Seven were deemed free of disease on post-imiquimod treatment scouting biopsies, while 2 were found to be clinically free of disease following confocal microscopy, indicating a tumor clearance rate of 90% with imiquimod treatment. One patient was found to have persistent residual disease following 2 rounds of imiquimod and was taken for an additional surgical excision after which they were deemed free of disease. Median follow-up duration from the onset of imiquimod therapy to the last clinic visit was 18 months, without any recurrences to date.
Conclusion: Imiquimod appears to demonstrate an encouraging tumor clearance among patients with persistent MMIS after surgery where further surgical resection may not be feasible. Although long-term durability has not been demonstrated in this study, a 90% tumor clearance rate is promising. J Drugs Dermatol. 2023;22(5): doi:10.36849/JDD.6987.